In metal connection in electrical and electronic devices, solder connection using a solder paste has been generally used, and in such a solder paste, a solder alloy containing lead has been conventionally used.
However, in view of environmental load, recently, use of lead has been required to be suppressed and thus, the development of a solder alloy containing no lead (lead-free solder alloy) has been promoted.
As such a lead-free solder alloy, for example, a tin-copper alloy, a tin-silver-copper alloy, a tin-silver-indium-bismuth alloy, a tin-bismuth alloy, and a tin-zinc alloy have been well known and among all, a tin-silver-copper alloy, a tin-silver-indium-bismuth alloy, and the like have been widely used.
To be specific, for example, for such a lead-free solder alloy, Patent Document 1 (Examples 45 to 46) below has proposed a lead-free solder alloy containing 1 to 4 mass % of Ag, 0.6 to 0.8 mass % of Cu, 1 to 5 mass % of Sb, 0.01 to 0.2 mass % of Ni, and the balance of Sn, and to be more specific, a lead-free solder alloy containing, for example, 3.4 mass % of Ag, 0.7 mass % of Cu, 3.2 mass % of Bi, 3.0 mass % of Sb, 0.01 mass % or 0.05 mass % of Co, 0.04 mass % of Ni, and the balance of Sn.